Tumor necrosis factor alpha (TNF-α) is a cytokine produced by numerous cell types, including monocytes and macrophages, that was originally identified based on its ability to induce the necrosis of certain mouse tumors. Subsequently, a factor termed cachectin, associated with cachexia, was shown to be identical to TNF-α. TNF-α has been implicated in the pathophysiology of a variety of other human diseases and disorders, including shock, sepsis, infections, autoimmune diseases, transplant rejection and graft-versus-host disease.
Because of the harmful role of human TNF-α (hTNF-α) in a variety of human disorders, therapeutic strategies have been designed to inhibit or counteract hTNF-α activity. In particular, antibodies that bind to, and neutralize, hTNF-α have been sought as a means to inhibit hTNF-α activity. Some of the earliest of such antibodies were mouse monoclonal antibodies (mAbs), secreted by hybridomas prepared from lymphocytes of mice immunized with hTNF-α (see e.g., U.S. Pat. No. 5,231,024 to Moeller et al.). While these mouse anti-hTNF-α antibodies often displayed high affinity for hTNF-α and were able to neutralize hTNF-α activity, their use in vivo has been limited by problems associated with the administration of mouse antibodies to humans, such as a short serum half-life, an inability to trigger certain human effector functions, and elicitation of an unwanted immune response against the mouse antibody in a human (the “human anti-mouse antibody” (HAMA) reaction).
In an attempt to overcome the problems associated with the use of fully murine antibodies in humans, murine anti-hTNF-α antibodies have been genetically engineered to be more “human-like.” For example, chimeric antibodies, in which the variable regions of the antibody chains are murine-derived and the constant regions of the antibody chains are human-derived, have been prepared (e.g., U.S. Pat. No. 5,698,195, herein incorporated by reference). Additionally, humanized antibodies, in which the hypervariable domains and a number of the framework residues of the antibody variable regions are murine-derived but the remainder of the variable regions and the antibody constant regions are human-derived, have also been prepared (e.g. U.S. Pat. No. 5,994,510 to Adair et al., herein incorporated by reference). However, because these antibodies still retain a substantial number of murine residues, they still may elicit an unwanted immune reaction, the human anti-chimeric antibody (HACA) reaction, especially when administered for prolonged periods (see e.g., Elliott, et al., (1994) Lancet 344:1125–1127; and Elliot, et al., (1994) Lancet 344:1105–1110).
Attempts have been made to further limit or eliminate the presence of murine sequences in anti-TNF-α antibodies. For example, human monoclonal autoantibodies against hTNF-α have been prepared using human hybridoma techniques (e.g., U.S. Pat. No. 5,654,407 to Boyle, herein incorporated by reference). However, these hybridoma-derived monoclonal autoantibodies were reported to have an affinity for hTNF-α that was too low to measure by conventional methods, were unable to bind soluble hTNF-α and were unable to neutralize hTNF-α-induced cytotoxicity (see Boyle, et al., (1993) Cell. Immunol. 152:556–581). Moreover, the success of the human hybridoma technique generally depends upon the natural presence in human peripheral blood of lymphocytes producing autoantibodies specific for hTNF-α.
An alternative to naturally-occurring human anti-hTNF-α antibodies would be a recombinant hTNF-α antibody. Recombinant human antibodies that bind hTNF-α with relatively low affinity (i.e., Kd of about 10−7 M) and a relatively fast dissociation rate (i.e., koff of about 10−2 s−1) have been described (Griffiths, A. D., et al. (1993) EMBO J. 12:725–734). However, because of their relatively fast dissociation kinetics, and relatively low affinity, these antibodies may not be suitable for therapeutic use. Additionally, recombinant human anti-hTNF-α antibodies with moderate binding affinities (Kd of about 6×10−10 M), dissociation rates (koff of about 8.8×10−5 s−1), association rates (kon of about 1.9×105 M−1s−1), and neutralization potential (IC50 of about 1.25×10−10) have been described (See, D2E7 antibody in U.S. Pat. No. 6,258,562, herein incorporated by reference).
Accordingly, what is needed, are TNF-α binding molecules with a high binding affinity, a high association rate, a low dissociation rate and improved neutralization properties with regard to human TNF-α, as well as TNF-α binding molecules with significantly reduced immunogenicity in humans.